A few first impressions.
Not claiming they are thought through very well, and also not having very strong feelings on them. Just shooting some thoughts and impressions at you.
1. At first I missed the 'stop' buttons, but I saw the clever solution that they appear when the progress bar is at the top or bottom.
2. The position of the preferences panel is not remembered, and opens top left every time.
3. The volume button is no longer horizontal and quite small, but is vertical and a bit larger (as it was in the past). I like that.
4. The 'checks' in the check-boxes don't look very refined and a bit cut-off at the left.
5. When toggling spectrum visualizations, sometimes the volume bar is not redrawn correctly:
6.
I would like to be able to select several options from the top 4 and have them visible in the panel at the same time. At this moment it is either/or?
Also I do not understand the difference between the 'dots' in front of the top 4, and the 'checks' at the two bottom options. I would assume that a dot could indicate either/or between choices, and for a check-box you could have several activated? If so, it should be the other way around here?
Also I see the sequence of the top 4 options rearranges when changed. I think I would prefer they kept their position.
6. At this moment we have a main panel, a left sidebar, and a right sidebar. That is rather easy to understand.
What I find that can be a little bit confusing that there also is a 'left main panel'. (that b.t.w. doesn't do anything in this alpha version? correct?)
Maybe it would be better to replace that with a 'sub-panel'? With the option to locate it left, right, bottom, top?
Then that might also be useful to improve on something that was often confusing to some users and was asked quite often: The 'artist information' panel that could be displayed at the bottom of the main panel, but often was not clear to users how to get it displayed.
Maybe that ' artist information' panel could then also be moved into this suggested 'sub-panel'?